WO2008085631A1

WO2008085631A1 - Dichloroethylene and co2 blowing agent blend for urethane foam

Info

Publication number: WO2008085631A1
Application number: PCT/US2007/086745
Authority: WO
Inventors: Ian A. Wheeler
Original assignee: Arkema Inc.
Priority date: 2007-01-05
Filing date: 2007-12-07
Publication date: 2008-07-17

Abstract

The present invention relates to a method of producing foam such as a closed cell, rigid polyurethane foam which employs CO2 as the predominate blowing agent and incorporates a dichloroethylene. The CO2 is preferably produced in situ via the reaction of water, in part B, and isocyanate, in part A. The water and the dichloroethylene are preferably incorporated into the polyol or B part of the components. It was found that including a dichloroethylene in the polyol or B part reduced the viscosity of the B part and provided for better flow of the B part in the production/mixing equipment. It also provides for better mixing of the B part and the A part which results in a more uniform foam. The inclusion of a dichloroethylene in the B part also enhances certain properties of the resulting foam such as brittleness and adhesion.

Description

DICHLOROETHYLENE AND CO₂ BLOWING AGENT BLEND FOR URETHANE FOAM

Field of The Invention

The present invention generally relates to improvements in the use of CO₂ as the predominate blowing agent in the preparation of foam such as rigid, closed cell urethane foam. More specifically, it relates to the use of a combination including water and a dichloro ethylene in the polyol component of urethane foam production. The water provides for the in situ formation of CO₂ blowing agent via reaction with the isocyanate component during foam production. The dichloroethylene provides for enhanced properties of both the polyol component and the resulting rigid polyurethane foam.

Background of The Invention

Polyurethane foams are widely known and used in many industries. Such foams are produced by reaction of an isocyanate with a polyol in the presence of various additives. Typically, one such additive is a blowing agent such as a chlorofluorocarbon (CFC) which vaporizes as a result of the reaction exotherm causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Alternatives to CFCs have been and continue to be a focus in industry. Production of water-blown foams, in which blowing is performed with CO₂ generated by the reaction of water with the isocyanate, has therefore become increasingly important

In the past, and in fact, in the earliest use of urethanes, carbon dioxide (CO₂) was used as a blowing agent for urethane foams. Such CO₂ was not supplied as a gas independently of the reaction but resulted from reacting a portion of the isocyanate with water. The remaining isocyanate portion was used to create part of the polymers. Historically speaking, it was common to provide hydroxyl-rich resins, and a small amount of water in part B which, when exposed to the isocyanate, in part A, would create the carbon dioxide blowing agent that resulted in the production of a polyurethane foam product.

In the production of rigid, closed sell insulating urethane foams, water is also used to lower the cost and to produce crosslinking isocyanurate groups that increase the rigidity of the foam. However, the presence of water can also produce brittle polymers. Brittle polymers can be detrimental in some applications as stresses during the use of the finished article can lead to breakdown of the foam. In addition, brittleness which develops early in the curing of the thermoset polymer can be an indication that the foam will exhibit poor adhesion to substrates. This can be an issue where the foam is used as a filler such as in a cabinet or a door cavity. In these aplications, adhesion to the facings is necessary to improve the structural integrity of the finished article. Thus, the production of closed cell insulating foams using CO₂ gas developed from the interaction of water and isocyanates has problems not present in the use of physical blowing agents such as chlorofluorocarbons.

The production of rigid closed cell foam using only water, to produce CO₂ gas, is also problematical because the water is difficult to disolve in the non-reactive ingredients such as catalysts, flame retardants and blowing agents, which are typically blended into the B side, the polyol side, of the blend. This increases the viscosity of the B side blend, which makes it more difficult to flow through pumps and pipes and more difficult to mix with the isocyanate, the A side blend. As the mixing of the two reactants, the A side and the B side, is exothermic and highly reactive, proper mixing is important. Problems during mixing can render the formulation inoperable in many applications.

While some water (to produce CO₂) is present in most closed cell polyurethane foam formulations, the level of CO₂ gas is typically less than about 50 mole percent of the foam cell gas, typically 5 to 50% depending on the application. The rest of the gas being a fluorochemcial such as a chlorofluorocarbon. Open cell foams are often blown with pure water, but these foams are inefficient in insulation applications, and flexible, high molecular weight polyols are used in such applications.

Summary of The Inventoin

The present invention relates to foam such as rigid, closed cell urethane foams. The foams are produced with CO₂ as the predominate blowing agent. The CO₂ blowing agent is formed in situ via the reaction of water and an isocyanate. The water is supplied as a part of the B side, or polyol side of the urethane foam production components. It was discovered that the additon of a dichloroethylene, preferably 1,2- trans-dichlroethylene, along with the water provides for enhanced properties of both the B side components as well as the foam produced. The addition of a dichloroethylene, such asl,2-trans-dichlroethylene to the B side along with water provides for a reduction in the visocity of the B side. This facilitates handling and mixing resulting in a more uniform foam. It also provides for a final foam product which is less brittle than one produced without the dichloroethylene.

Detailed Description of The Invention

The present invention relates to a method of producing foam such as closed cell, rigid polyurethane foam. The present invention comprises employing CO₂ as the predominate blowing agent and incorporating a dichloroethylene into the B part. The CO₂ is preferably produced in situ via the reaction of water, in the B part, and isocyanate, in the A part. In an alternative process, the CO₂ could be added independently during foam production such as into an extruder during mixing of the A and B parts. The water and the dichloroethylene are preferably incorporated into the polyol or B part of the components. It was found that including a dichloroethylene in the polyol or B part reduced the viscosity of the B part. This provides for better flow of the B part in the production/mixing equipment. It also provides for better mixing of the B part and the A part which results in a more uniform foam. The inclusion of a dichloroethylene such as 1 ,2-trans-dichloroethylene (TDCE) in the B part also enhances certain properties of the resulting foam such as brittleness and adhesion. The TDCE can also be added to the A part.

Rigid polyurethane foam produced with CO₂ alone is difficult to produce with high closed cell content and is often very friable, or brittle. The inclusion of TDCE in the combination of the present invention was found to improve the formulation latitude while providing high closed cell content and reducing the initial surface friability of the foam. The reduction in friability indicates improved adhesion charteristics of the foam that is beneficial in applications such as panels, appliances or refrigerated containers.

The method of the present invetion comprises using TDCE and water to produce foam such as closed cell rigid urethane foam without the use of other physical blowing agents. The concentration of water and TDCE in the blowing agent are typicaly kept constant and can be varied from about 15 to 30 milliliters of blowing agent per gram of foam. Typically, B side blends that include high levels of water have high viscosities. The viscosity of the B-side blends of the present invention decrease as the level of TDCE is increased. This viscosity decrease enhances handling of the B side blend such as during pumping as well as during mixing with the A side. The formulation of the present invention was compared to a formulation that used only water to produce 100% CO₂ blowing agent. The B-side blends of the formulation of the present invetion can also include typical components such as flame retardants, catalysts and surfactants, as well as the water and TDCE.

Illustrative of suitable polyols for use in the present invention are aromatic polyester polyol by itself or the combination of aromatic polyester polyol and polyether polyol. Examples of aromatic polyester polyol are for example polyols derived from phthalic anhydride, scrap of polyethylene terephthalate, dimethyl terephthalate process residue and the like. Examples of polyether polyol are for example amino polyol of ethylenediamine, tolylenediamine, triethanolamine, Mannich condensate and the like with the addition of alkylene oxide such as ethylene oxide, propylene oxide and the like.

Illustrative of suitbale of polyisocyanates useful in the present invention are polymethylene polyphenyl isocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,6-dimethyl-l,3- phenylenediisocyanate, 4,4'-dibenzyl diisocyanate, 9,10-anthracenediisocyanate, 4,3'- dimethyl-4,4'-diphenyl diisocyanate, xylylene diisocyanate, 2,6-dimethyl-4,4'- diphenyl diisocyanate, 2,4'-diphenylmethane diisocyanate and the like.

Polymerization catalysts including amine catalyst and metal catalyst can be employed in the polymerization process.

Optional additives can include flame retardants which can include phosphates such as trimethylphosphate, triethylphosphate, trischloropropylphosphate and the like, and the amount to be added is preferably 20 to 40 parts by weight based on 100 parts by weight of polyol. Phosphate and the like give plasticity to urethane resin and thus have the effects on improving the friable that is the shortcoming of rigid polyurethane foam to be formed with water as the blowing agent and enhancing the adhesion, but if the amount of phosphate exceeds 40 parts by weight, the strength tends to decrease due to the immoderate plasticity.

Other optional additives that are used in the preparation of rigid polyurethane foam can be used in the present invention. For example, polyoxyalkylene type foam stabilizer such as polyoxyalkylenealkylether and the like, silicone type foam stabilizer such as organosiloxane and the like, compatibilizing agents such as oxyethylenealkylphenol, viscosity reducing agents, colorants, stabilizers and the like can be used in the preparation of rigid polyurethane foam according to the present invention.

The present invention will now be further described with reference to a number of specific examples which are to be regarded as illustrative and not as restricting the scope of the present invention. All percentages stated herein are by weight.

Examples

In order to demonstrate how TDCE can effect closed cell rigid foam without the use of other physical blowing agents, a formulation was developed using TDCE and water only. This was compared to a formulation that used only water to produce 100% CO₂ blowing agent. A series of B-side blends were prepared each containing polyols, flame retardants, catalysts and surfactants, as well as water and TDCE. The total moles of water and TDCE were kept constant but the mole ratio of the water and the TDCE were varied from 0, 50 and 75 mole% TDCE. It was found that the viscosity of the blends was significantly reduced as the level of TDCE increased.

Foams were produced using a standard hand mix method. The foam was made allowing it to free rise. The same method of foam production was maintained for all the samples. The foam's free rise density was tested and a Mobile 45 fire test was performed on four samples from each of the foams.

The results of the Mobile 45 fire test showed a definite trend of reduced weight loss with increased TDCE level. The 0% TDCE gave an average weight loss of 19.98% the 50% TDCE gave an average of 13.84% weight loss and the 75% TDCE gave an average of 10.69% weight loss.

During our initial evaluation it was observed that the use of TDCE improved the adhesion of foam to a substrate. It was found that the reduction in initial surface friability can be an indication of improved adhesion properties. Relative Surface friability can be determined by weight loss in a tumble test. It was observed that the 0% TDCE foam had an initial surface friability of 5.9% while a formulation with 20% TDCE gave <1% initial surface friability.

A 100% CO₂ blown polyurethane foam based on common industry practice was prepared. The formulation had a 110 index and a total blowing agent level of 18.7 ml/g. The fire retardant level was 8.24% of total foam. A polyol blend of Siltech 425LV (available from Siltech Corp.), Dow Varnol 391 (available from Dow) and Terate 2541 (available from Invista) in a 19/9/9 ratio was used. The formulation included 0.6% Tegostab B8465 silicone surfactant (available from Goldschmidt) with Bl-13 and Polycat 8 amine catalysts at 0.3 and 0.6% of the total foam (available from Air Products). The isocyanate used was Rubinate M (available from Huntsman).

The foam was produced using the hand mix method blending the premixed B- side (polyols, surfactant, catalyst and blowing agents) with the Rubinate M A-side. The ratio of polyol to isocyanate was varied as the ratio of CO₂ to TDCE was varied. For 100% CO₂, a ratio 0.75: 1:: polyol: isocyanate was employed. For 50% CO₂: 50% TDCE a ratio of 1 :1 :: polyol:isocyanate was employed. For 25% CO₂:75% TDCE, a ratio of 1.2: 1 :: polyol: isocyanate was employed. The foam was allowed to cure for 24 hours prior to being cut for density determination and for Mobil 45 fire testing. In the Mobile 45 fire testing, 100% CO₂ blown foam gave a 19.8% weight loss while a foam with 50/50 CO₂ATDCE gave a 13.8% weight loss and a foam with 25% CO₂ with 75% TDCE gave a 10.7% weight loss.

The viscosity of the B-side blend incorporating the different ratios of CO₂ to TDCE was measured using a Brookfield viscometer. The 25%TDCE:75% CO₂ showed a 33% reduction in viscosity over the 100% CO₂ blend and the 50% CO₂:50% TDCE showed a 42% reduction in viscosity.

Initial friability testing was done using a modification of the ASTM C 421-95 test. The samples were cut 10 minutes after producing the sample and the foam skin was kept on the samples. The 100% CO₂ blown foam gave a weight loss of 5.9% while the TDCE containing foam gave less than 1% weight loss.

While the present invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

Claims

WE CLAIM:

1. A method of preparing a polyurethane foam comprising reacting an organic polyisocyanate and a polyol in the presence of a blowing agent comprising CO₂, formed in situ via the reaction of water and said polyisocyanate, and a dichloroethylene.

2. The method of claim 1 wherein said dichloroethylene is 1,2-trans- dichloroethylene.

3. The method of claim 1 wherein said polyurethane foam is a rigid closed cell foam.

4. The method of claim 1 wherein said water and said dichloroethylene are combined with said polyol prior to reacting with said polyisocyanate.

5. The method of claim 4 wherein said combination of water, dichloroethylene and polyol further includes a catalyst, a fire retardant, a surfactant or mixtures thereof.